Natural variations in brain phenylethanolamine-N-methyltransferase activity during different phases of the oestrous cycle: Effect of chronic dexamethasone treatment.

Abstract

Abstract-The activity of phenylethanolamine-N-methyltransferase (PNMT) was studied in the hypothalamus, hypophysis, striatum and the rest of the brain during the four different phases of the oestrous cycle of the rat. The oestrous phase was marked by high level of enzyme activity in all the regions except the hypophysis. The hypophysis showed maximum increase in activity at the metoestrous phase of the oestrous cycle.Chronic treatment of rats with dexamethasone for 10 days led to decreased level of PNMT activity in the hypophysis, hypothalamus and the rest of brain. These decreases were important in the hypothalamus and the hypophysis which represented only 25 and 20% of the control activity after dexamethasone administration.